High speed cement bond logging and interactive targeted intervention

ABSTRACT

A method for cement bond logging and targeted intervention, including lowering a cylindrical n×m array of ultrasound (US) transducers into a well, firing the US transducers to transmit US signals into a well casing, converting reflected US signals received by the transducers into electronic form and transmit the converted signals to a control unit, analyzing the converted signals to detect holidays, if a holiday is detected, determining a position and angle of the holiday with respect to the transducers, and applying a high intensity focused ultrasound (HIFU) signal to the well casing to fill the holiday.

CROSS REFERENCE TO RELATED UNITED STATES APPLICATIONS

This application claims priority from “Device for High Speed Cement Bond Logging and interactive Targeted intervention”, U.S. Provisional Application No. 61/619,026 of Barnes, et al., filed Apr. 2, 2012, the contents of which are herein incorporated by reference in their entirety.

TECHNICAL FIELD

This application is directed to the application of imaging techniques for monitoring cement bond formation during curing.

DISCUSSION OF THE RELATED ART

When completing a well, such as an oil well or a water well, the well casing is typically stabilized through the introduction of cement, potentially with additives, into the annulus formed between the borehole and the casing. The primary function of this activity is to enforce zonal isolation. That is, the cement forms a seal that prevents communication (leaks) between different formations as well as with respect to the surface.

In the process of cementing, “holidays” (cavities) may form between the casing and formation. These holidays may be detected though standard cement bond logging techniques and ameliorated after the cement has cured through a secondary cementing process known as squeezing. Squeezing is an expensive, invasive method in which the casing is perforated and new cement forced in to displace the holidays.

SUMMARY

Exemplary embodiments of the invention as described herein generally include improvements to the process of cementing that can be combined into one piece of equipment.

According to an aspect of the invention, there is provided a method for cement bond logging and targeted intervention, including lowering a cylindrical n×m array of ultrasound (US) transducers into a well, firing the US transducers to transmit US signals into a well casing, converting reflected US signals received by the transducers into electronic form and transmit the converted signals to a control unit, analyzing the converted signals to detect holidays, if a holiday is detected, determining a position and angle of the holiday with respect to the transducers, and applying a high intensity focused ultrasound (HIFU) signal to the well casing to fill the holiday.

According to a further aspect of the invention, multiple simultaneous US signals are transmitted into the well casing.

According to a further aspect of the invention, the US transducers are fired according to a schedule that minimizes interference among the transducers.

According to a further aspect of the invention, the HIFU signal is focused upon a point in an annulus formed between a borehole of the well and the well casing.

According to a further aspect of the invention, the converted signals are analyzed by classifiers trained to detect holidays.

According to a further aspect of the invention, the HIFU signal is applied manually.

According to a further aspect of the invention, the HIFU signal is automatically applied by a control program.

According to another aspect of the invention, there is provided a system for cement bond logging and targeted intervention, including a cylindrical n×m array of solid state ultrasound (US) transducers, a connector that connects the transducer array to a motorized winch, and a control program of instructions in signal communication with the transducer array and executable by a computer tangibly embodied in one or more computer readable program storage devices that perform method steps for cement bond logging and targeted intervention. The method includes lowering the cylindrical n×m array of ultrasound (US) transducers into a well, firing the US transducers to transmit US signals into a well casing, converting reflected US signals received by the transducers into electronic form and transmit the converted signals to the control program, analyzing the converted signals to detect holidays, if a holiday is detected, determining a position and angle of the holiday with respect to the transducers, and applying a high intensity focused ultrasound (HIFU) signal to the well casing to fill the holiday.

According to a further aspect of the invention, the cylindrical n×m array of US transducers are arranged about a device axis.

According to a further aspect of the invention, the device contains a plurality of levels of US transducer.

According to a further aspect of the invention, the transducer array includes transducers for imaging the holidays, and transducers for applying the HIFU signal.

According to a further aspect of the invention, the signal communication between the control program of instructions and the transducer array comprises a wireless connection.

According to a further aspect of the invention, the signal communication between the control program of instructions and the transducer array comprises a wire included with the connector.

According to another aspect of the invention, there is provided a non-transitory program storage device readable by a computer, tangibly embodying a program of instructions executed by the computer to perform the method steps for cement bond logging and targeted intervention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) depicts a standard US bond logging configuration, in which the transducer rotates around a central axis.

FIG. 1( b) depicts a design which does not rotate but instead has fixed arrays of transducers, according to an embodiment of the invention.

FIG. 2 is a flow chart of an exemplary method for improving the process of cementing, according to an embodiment of the invention.

FIG. 3 is a block diagram of an exemplary computer system for implementing a method for improving the process of cementing, according to an embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the invention as described herein generally include systems for improving the process of cementing, while the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

As used herein, the term “image” refers to multi-dimensional data composed of discrete image elements (e.g., pixels for 2-dimensional images and voxels for 3-dimensional images). The image may be, for example, a medical image of a subject collected by computer tomography, magnetic resonance imaging, ultrasound, or any other medical imaging system known to one of skill in the art. The image may also be provided from non-medical contexts, such as, for example, remote sensing systems, electron microscopy, etc. Although an image can be thought of as a function from R³ to R or R⁷, the methods of the inventions are not limited to such images, and can be applied to images of any dimension, e.g., a 2-dimensional picture or a 3-dimensional volume. For a 2- or 3-dimensional image, the domain of the image is typically a 2- or 3-dimensional rectangular array, wherein each pixel or voxel can be addressed with reference to a set of 2 or 3 mutually orthogonal axes. The terms “digital” and “digitized” as used herein will refer to images or volumes, as appropriate, in a digital or digitized format acquired via a digital acquisition system or via conversion from an analog image.

Exemplary embodiments of the invention include a method for rapid cement bond logging using tightly packed arrays of ultrasonic transducers that is fast enough to facilitate the logging of the cement immediately after it has been introduced along the entirety of the casing in a short period of time. Given this ability to detect holidays quickly, exemplary embodiments of the invention can remotely “pulse” or “vibrate” the cement in regions behind the casing in a targeted manner using High Intensity Focused Ultrasound (HIFU). This may cause the cement to settle, filling in the holidays before the cement sets. This remote pulsing may be both localized and directional so as not to disturb the curing process in other regions of the well. Finally, in other exemplary embodiments of the invention, these improvements may be combined into another improvement, the interactive removal of holidays. In this scenario, the cement bond log readings are transmitted to the surface where an engineer can determine the location, duration, strength and frequency of HIFU pulses to push the cement towards a particular location.

Note that for practical reasons the ultrasound (US) transducers for logging and the US transducers for HIFU would likely not be one in the same, as the logging transducers produce only enough power for imaging purposes.

High Speed Cement Bond Logging using Multiple US Transducers

Current standard cement bond loggers that use ultrasound employ a range of from one to a handful of transducers attached to a string that can be rotated around the central axis of the string to scan the casing at a particular level. According to an embodiment of the invention, an n×m cylindrical array of solid state US transducers are packed around a device axis, so that rotation is not necessary. This configuration significantly speeds up logging. Multiple simultaneous beams can be formed, and the beams can be electronically steered. Indeed, other embodiments could include multiple levels of transducers. The transducer array can be attached to a connector such as cable, chain, or rope attached to a motorized winch and can be lowered into the well under the control of a control software program. In other embodiments, the winch can be manually controlled by an operator. The transducers are in signal communication with the control program either wirelessly or via wire included with the connector to which the transducers are attached. A firing schedule of the transducers can be employed to prevent interference between the transducers. FIG. 1( a) depicts a standard US bond logging configuration, in which a single transducer 11 connected to the connector 13 rotates around a central axis. FIG. 1( b) depicts a design according to an embodiment of the invention which does not rotate but instead has fixed arrays of transducers 12 connected to the connector 13.

High Intensity Focused Ultrasound for Remote Cement Agitation

High Intensity Focused Ultrasound (HIFU) is a technique in which ultrasonic sound waves are focused at a particular point, similar to the way in which light is focused. That focal point may be relatively far (1-2 feet) from the source transducers and may be separated from the transducers by a barrier which attenuates the waves to some extent but allows them to pass through.

According to an embodiment of the invention, with enough energy, ultrasound waves can be transmitted through a well casing to focus on a point in the annulus. In this way, cement positioned above a holiday can be vibrated or “pushed” to settle and displace the void below it. The effect would be of shaking the region around an isolated bubble to force the bubble to the surface.

Note that it is possible to push through a wide range of angles using HIFU. The beam angle, measured as the angle between the surface normal of the casing and the beam direction vector, is limited by the acceptance angle of the elements in the transducer array. Smaller elements have larger acceptance angle, down to an element dimension of about a half a wavelength where it is asymptotically approaching a limit. Current transducers have an element pitch of about 0.3 wavelengths by about 0.6 wavelengths, and can steer to at about 55 degrees in one direction and 45 degrees in the orthogonal direction.

It should be noted that this agitating can be done without HIFU by hammering on the casing itself. However, this would affect the cement in a much larger region and disrupt the curing process along the well, particularly in parts that have already been cleared of holidays. By targeting the agitation to a point beyond the casing, in the annulus, embodiments of the invention have minimal influence and allow the holiday-cleared cement to set.

Interactive Targeting

According to another embodiment of the invention, the US device has a communication line running to the surface that allows a real time visualization of information from the logging transducers. An engineer may lower the US device to the bottom of the well just after the cement is delivered and starts raising the US device while searching for holidays. Note that these holidays can be detected automatically by classifiers trained for this purpose. If a holiday is detected, the position and angle for which to apply the HIFU can be automatically determined from the US signal. The engineer applies the HIFU to remove the holiday and continues raising the casing string until it reaches the cement top. Alternatively, the HIFU can be automatically applied by control software. The presence of displacement fluid in the casing should not be a problem and could serve as a medium to help conduct the sound waves.

A flowchart of a method for high speed cement bond logging and interactive targeted intervention according to an embodiment of the invention is presented in FIG. 2. Referring now to the figure, a method begins at step 20 by lowering a cylindrical n×m array of solid state US transducers into a well. At step 21, the transducers are fired to transmit ultrasound signals into the well casing, and the reflected signals are received at step 22, converted to electronic form and transmitted to a control unit at the surface. At step 23, the converted US signals are analyzed by image classifiers being executed by the control unit. If a holiday is detected by a classifier, the controlling software and determine at step 24 its position and angle with respect to the transducers, and apply an HIFU signal at step 25 to fill in the holiday.

System Implementations

It is to be understood that the present invention can be implemented in various forms of hardware, software, firmware, special purpose processes, or a combination thereof. In one embodiment, the present invention can be implemented in software as an application program tangible embodied on a computer readable program storage device. The application program can be uploaded to, and executed by, a machine comprising any suitable architecture.

FIG. 3 is a block diagram of an exemplary computer system for implementing a method for improving the process of cementing according to an embodiment of the invention. Referring now to FIG. 3, a computer system 31 for implementing the present invention can comprise, inter alia, a central processing unit (CPU) 32, a memory 33 and an input/output (I/O) interface 34. The computer system 31 is generally coupled through the I/O interface 34 to a display 35 and various input devices 36 such as a mouse and a keyboard. The support circuits can include circuits such as cache, power supplies, clock circuits, and a communication bus. The memory 33 can include random access memory (RAM), read only memory (ROM), disk drive, tape drive, etc., or a combinations thereof. The present invention can be implemented as a routine 37 that is stored in memory 33 and executed by the CPU 32 to process the signal from the signal source 38. As such, the computer system 31 is a general purpose computer system that becomes a specific purpose computer system when executing the routine 37 of the present invention.

The computer system 31 also includes an operating system and micro instruction code. The various processes and functions described herein can either be part of the micro instruction code or part of the application program (or combination thereof) which is executed via the operating system. In addition, various other peripheral devices can be connected to the computer platform such as an additional data storage device and a printing device.

It is to be further understood that, because some of the constituent system components and method steps depicted in the accompanying figures can be implemented in software, the actual connections between the systems components (or the process steps) may differ depending upon the manner in which the present invention is programmed. Given the teachings of the present invention provided herein, one of ordinary skill in the related art will be able to contemplate these and similar implementations or configurations of the present invention.

While the present invention has been described in detail with reference to exemplary embodiments, those skilled in the art will appreciate that various modifications and substitutions can be made thereto without departing from the spirit and scope of the invention as set forth in the appended claims. 

What is claimed is:
 1. A method for cement bond logging and targeted intervention, comprising the steps of: lowering a cylindrical n×m array of ultrasound (US) transducers into a well; firing the US transducers to transmit US signals into a well casing; converting reflected US signals received by the transducers into electronic form and transmit the converted signals to a control unit; analyzing the converted signals to detect holidays; if a holiday is detected, determining a position and angle of the holiday with respect to the transducers; and applying a high intensity focused ultrasound (HIFU) signal to the well casing to fill the holiday.
 2. The method of claim 1, wherein multiple simultaneous US signals are transmitted into the well casing.
 3. The method of claim 2, wherein the US transducers are fired according to a schedule that minimizes interference among the transducers.
 4. The method of claim 1, wherein the HIFU signal is focused upon a point in an annulus formed between a borehole of the well and the well casing.
 5. The method of claim 1, wherein the converted signals are analyzed by classifiers trained to detect holidays.
 6. The method of claim 1, wherein the HIFU signal is applied manually.
 7. The method of claim 1, wherein the HIFU signal is automatically applied by a control program.
 8. A non-transitory program storage device readable by a computer, tangibly embodying a program of instructions executed by the computer to perform the method steps for cement bond logging and targeted intervention, the method comprising the steps of: lowering a cylindrical n×m array of ultrasound (US) transducers into a well; firing the US transducers to transmit US signals into a well casing; converting reflected US signals received by the transducers into electronic form and transmit the converted signals to a control unit; analyzing the converted signals to detect holidays; if a holiday is detected, determining a position and angle of the holiday with respect to the transducers; and applying a high intensity focused ultrasound (HIFU) signal to the well casing to fill the holiday.
 9. The method of claim 8, wherein multiple simultaneous US signals are transmitted into the well casing.
 10. The method of claim 9, wherein the US transducers are fired according to a schedule that minimizes interference among the transducers.
 11. The method of claim 8, wherein the HIFU signal is focused upon a point in an annulus formed between a borehole of the well and the well casing.
 12. The method of claim 8, wherein the converted signals are analyzed by classifiers trained to detect holidays.
 13. The method of claim 8, wherein the HIFU signal is applied manually.
 14. The method of claim 8, wherein the HIFU signal is automatically applied by a control program.
 15. A system for cement bond logging and targeted intervention, comprising a cylindrical n×m array of solid state ultrasound (US) transducers; a connector that connects the transducer array to a motorized winch; and a control program of instructions in signal communication with the transducer array and executable by a computer tangibly embodied in one or more computer readable program storage devices that perform the method steps for cement bond logging and targeted intervention, the method comprising the steps of: lowering the cylindrical n×m array of ultrasound (US) transducers into a well; firing the US transducers to transmit US signals into a well casing; converting reflected US signals received by the transducers into electronic form and transmit the converted signals to the control program; analyzing the converted signals to detect holidays; if a holiday is detected, determining a position and angle of the holiday with respect to the transducers; and applying a high intensity focused ultrasound (HIFU) signal to the well casing to fill the holiday.
 16. The system of claim 15, wherein the cylindrical n×m array of US transducers are arranged about a device axis.
 17. The system of claim 16, wherein the device contains a plurality of levels of US transducer.
 18. The system of claim 15, wherein the transducer array includes transducers for imaging the holidays, and transducers for applying the HIFU signal.
 19. The system of claim 15, wherein the signal communication between the control program of instructions and the transducer array comprises a wireless connection.
 20. The system of claim 15, wherein the signal communication between the control program of instructions and the transducer array comprises a wire included with the connector. 